The subject matter disclosed herein relates to braze methods and components and, more specifically, to braze methods and components with heat resistant materials.
A wide variety of industry components may undergo a braze operation to add new material, modify existing material, modify the shape of a component, join multiple components together, or otherwise alter the original component. The braze operation may generally comprise heating a filler metal above its melting temperature (i.e., above its liquidus temperature) while disposed on a base substrate (i.e., the original component) and subsequently cool the materials to join the filler metal and the base substrate together.
Various turbine components may, for example, undergo one or more braze cycles during original manufacture or modification pre or post utilization in a turbine. Some particular turbine components may also possess very high strength, toughness and/or other physical properties to facilitate sustained operation. Turbine components such as buckets (blades), nozzles (vanes), and other hot gas path components and combustions components of industrial and aircraft gas turbine engines may be formed of nickel, cobalt or iron-base superalloys with suitable mechanical and environmental properties.
Braze operations are typically limited to those surfaces requiring modification. For example, surfaces subject to contact with adjacent components during turbine operation, such as the z-notch surface of a turbine bucket shroud, may be more prone to wear or the like and therefore may be more likely to undergo future braze operations. However, as turbine components increase in size to increase overall power output, surfaces that were not previously known to experience contact during operation may also experience wear. For example, larger turbine components may be subject to increased oscillation during turbine start-up. This oscillation may cause increased contact to surfaces including seal rails, z-notch adjacent surfaces and angel wings, collectively referred to herein as non-z-notch contact surfaces. Modification of these surfaces, such as after extended use, may become laborious and costly. Welding, for example, may be difficult due to the relative small amount of material available to disperse heat to prevent cracking.
Moreover, in even some instances, because the efficiency of a turbomachine can be at least partially dependent on its operating temperatures, there may be a demand for components such as turbine buckets and nozzles to be capable of withstanding increasingly higher temperatures. As the maximum local temperature of a superalloy component approaches the melting temperature of the superalloy, forced air cooling may become necessary. For this reason, airfoils of gas turbine buckets and nozzles may include complex cooling schemes in which air, typically bleed air, is forced through internal cooling passages within the airfoil and then discharged through cooling holes at the airfoil surface to transfer heat from the component. Cooling holes can also be configured so that cooling air serves to film cool the surrounding surface of the component. Depending on the manufacturing operation, one or more portions of the cooling passages may need to be stopped off, such as by using braze or pre-sintered preforms, to force the flow of air in the appropriate direction. However, the braze or pre-sintered preform may be subject to elevated temperatures during heat treatment operations such as material rejuvenation processes, repair processes, or the like. These elevated temperatures may cause the braze or pre-sintered preform to partially melt or otherwise change shape (e.g., slump) thereby creating additional manufacturing operations.
Accordingly, alternative braze methods and components with heat resistant materials would be welcome in the art.